fix: use cached git service snapshots for fetchWorkspaces instead of shelling out

describeWorkspaceRecordWithGitData was calling buildProjectPlacement → getCheckoutStatusLite
which spawned 3-4 sequential git child processes per workspace. With 8 active workspaces
and event loop pressure from running agents, this caused fetchWorkspaces to take 35-45s.

Now uses workspaceGitService.getSnapshot() which returns instantly from cache (warm path)
or awaits the git service's own concurrency-managed refresh (cold path).

packages/server/src/server/session.ts

@@ -114,6 +114,7 @@ import type {
 import { AgentStorage, type StoredAgentRecord } from "./agent/agent-storage.js";
 import {
   buildProjectPlacementForCwd,
+  checkoutLiteFromGitSnapshot,
   detectStaleWorkspaces,
   deriveProjectKind,
   deriveProjectRootPath,
@@ -5406,26 +5407,17 @@ export class Session {
     projectRecord?: PersistedProjectRecord | null,
   ): Promise<WorkspaceDescriptorPayload> {
     const base = await this.describeWorkspaceRecord(workspace, projectRecord);
-    let displayName = workspace.displayName;
-    try {
-      const placement = await this.buildProjectPlacement(workspace.cwd);
-      displayName = deriveWorkspaceDisplayName({
-        cwd: workspace.cwd,
-        checkout: placement.checkout,
-      });
-    } catch {
-      // Fall back to the persisted label if checkout metadata is unavailable.
-    }
+    const snapshot = await this.workspaceGitService.getSnapshot(workspace.cwd);
 
-    let snapshot: WorkspaceGitRuntimeSnapshot | null = null;
-    snapshot = this.workspaceGitService.peekSnapshot(workspace.cwd);
+    const checkout = checkoutLiteFromGitSnapshot(workspace.cwd, snapshot.git);
+    const displayName = deriveWorkspaceDisplayName({ cwd: workspace.cwd, checkout });
 
     return {
       ...base,
       name: displayName,
-      diffStat: snapshot?.git.diffStat ?? null,
-      gitRuntime: snapshot ? this.buildWorkspaceGitRuntimePayload(snapshot) : undefined,
-      githubRuntime: snapshot ? this.buildWorkspaceGitHubRuntimePayload(snapshot) : undefined,
+      diffStat: snapshot.git.diffStat ?? null,
+      gitRuntime: this.buildWorkspaceGitRuntimePayload(snapshot),
+      githubRuntime: this.buildWorkspaceGitHubRuntimePayload(snapshot),
     };
   }
 

packages/server/src/server/session.workspaces.test.ts

@@ -1845,9 +1845,7 @@ describe("workspace aggregation", () => {
     });
     const workspaceGitService = createNoopWorkspaceGitService();
     workspaceGitService.peekSnapshot = vi.fn(() => runtimeSnapshot);
-    workspaceGitService.getSnapshot = vi.fn(async () => {
-      throw new Error("fetch_workspaces should not trigger per-workspace refreshes");
-    });
+    workspaceGitService.getSnapshot = vi.fn(async () => runtimeSnapshot);
     workspaceGitService.subscribe = vi.fn(async () => ({
       initial: runtimeSnapshot,
       unsubscribe: () => {},
@@ -1901,8 +1899,7 @@ describe("workspace aggregation", () => {
       | { type: "fetch_workspaces_response"; payload: any }
       | undefined;
 
-    expect(workspaceGitService.peekSnapshot).toHaveBeenCalledWith("/tmp/repo");
-    expect(workspaceGitService.getSnapshot).not.toHaveBeenCalled();
+    expect(workspaceGitService.getSnapshot).toHaveBeenCalledWith("/tmp/repo");
     expect(response?.payload.entries).toEqual([
       expect.objectContaining({
         id: "/tmp/repo",
@@ -1953,9 +1950,7 @@ describe("workspace aggregation", () => {
     });
     const workspaceGitService = createNoopWorkspaceGitService();
     workspaceGitService.peekSnapshot = vi.fn(() => runtimeSnapshot);
-    workspaceGitService.getSnapshot = vi.fn(async () => {
-      throw new Error("workspace updates should use passive workspace git snapshots");
-    });
+    workspaceGitService.getSnapshot = vi.fn(async () => runtimeSnapshot);
 
     const session = createSessionForWorkspaceTests({
       workspaceGitService,
@@ -2008,8 +2003,7 @@ describe("workspace aggregation", () => {
       skipReconcile: true,
     });
 
-    expect(workspaceGitService.peekSnapshot).toHaveBeenCalledWith("/tmp/repo");
-    expect(workspaceGitService.getSnapshot).not.toHaveBeenCalled();
+    expect(workspaceGitService.getSnapshot).toHaveBeenCalledWith("/tmp/repo");
     expect(emitted).toContainEqual({
       type: "workspace_update",
       payload: {

packages/server/src/server/workspace-registry-model.ts

@@ -137,6 +137,50 @@ export function deriveWorkspaceKind(checkout: ProjectCheckoutLitePayload): Persi
   return checkout.isPaseoOwnedWorktree ? "worktree" : "local_checkout";
 }
 
+export function checkoutLiteFromGitSnapshot(
+  cwd: string,
+  git: {
+    isGit: boolean;
+    currentBranch: string | null;
+    remoteUrl: string | null;
+    repoRoot: string | null;
+    isPaseoOwnedWorktree: boolean;
+    mainRepoRoot: string | null;
+  },
+): ProjectCheckoutLitePayload {
+  if (!git.isGit) {
+    return {
+      cwd,
+      isGit: false,
+      currentBranch: null,
+      remoteUrl: null,
+      worktreeRoot: null,
+      isPaseoOwnedWorktree: false,
+      mainRepoRoot: null,
+    };
+  }
+  if (git.isPaseoOwnedWorktree && git.mainRepoRoot) {
+    return {
+      cwd,
+      isGit: true,
+      currentBranch: git.currentBranch,
+      remoteUrl: git.remoteUrl,
+      worktreeRoot: git.repoRoot ?? cwd,
+      isPaseoOwnedWorktree: true,
+      mainRepoRoot: git.mainRepoRoot,
+    };
+  }
+  return {
+    cwd,
+    isGit: true,
+    currentBranch: git.currentBranch,
+    remoteUrl: git.remoteUrl,
+    worktreeRoot: git.repoRoot ?? cwd,
+    isPaseoOwnedWorktree: false,
+    mainRepoRoot: null,
+  };
+}
+
 export async function detectStaleWorkspaces(
   input: DetectStaleWorkspacesInput,
 ): Promise<Set<string>> {